If you’re wanting to do stuff like festivals, you’d probably want to find a clown school.

But doing it as a volunteer, all you really need is a suit, a face, and skills. Juggling, balloon making, card tricks, etc. Then you reach out to facilities and work out the arrangements for a performance. Hospitals can be a tad restrictive about who gets to do shows for pediatric wards, so you’ll likely want to try nursing homes first and build up a local rep.

You can also try to hook up with local sideshow type troupes. Clowns aren’t always welcome, but you can usually pick up some skills if you’re honest about it. The fire performers won’t teach you, but jugglers and magicians will usually share some basics as long as you aren’t trying to shaft them with it.